Before beginning your install of WebSphere Portal you should consider how to
use the environment in order to achieve ideal performance.
Topics to
consider include:
- Choosing between 32-bit and 64-bit JVMs
- Use of hardware multithreading, also known as Simultaneous Multithreading
or Hyper-Threading
32-BIT AND 64-BIT CONSIDERATIONS
The choice of a 32-bit or 64-bit Java™ Virtual Machine (JVM)
involves some trade-offs. The key advantage of a 64-bit JVM is its vastly
larger address space. Heap sizes of 2.5GB or larger can be practical on modern
server systems. This can be a significant benefit for applications with high
memory demands.
A 64-bit JVM does have disadvantages as well. Machine instructions and
memory references in a 64-bit JVM are larger than in a 32-bit JVM. This means
that Java objects, which typically contain multiple memory references, are
larger in a 64-bit JVM than compared to a 32-bit JVM. Therefore a 64-bit JVM
will need a larger heap than a 32-bit JVM for the same population of
objects.
The increased size of instructions and memory references imposes a second
performance penalty. They increase the demand on the memory subsystem of the
system, causing more cache misses and a higher demand for memory bandwidth. As
a result, executing a set of operations in a 64-bit JVM can be slower than
executing the same operations in a 32-bit JVM.
When considering a deployment of WebSphere Portal 6.1, consider the memory
demands your applications will have. If you expect a high demand for memory,
the best performance will probably come from a 64-bit JVM. On the other hand,
if the memory demand is lower, a 32-bit JVM is likely to give superior
performance.
HARDWARE MULTITHREADING (HYPER-THREADING)
Many modern processor architectures support hardware multithreading.
For example, this is known as Hyper-Threading (HT) on Intel processors and
Simultaneous Multithreading (SMT) on Power-series processors. Our experience is
that using hardware multithreading provides an improvement in capacity in all
of the scenarios and platforms reported in this report, so we would recommend
its use on platforms where this is an option.
Before beginning your installation of WebSphere Portal consider whether to use 32-bit or 64-bit JVMs and evaluate hardware multithreading benefits.